The switching of circuits for currents with a higher output, which is to say at high voltages and/or high currents, is a challenge in the entire field of electrical engineering. This problem is encountered in particular when switching off high direct currents, which when compared to alternating currents, do not have zero crossings that can form with a sufficiently high voltage a light arc, which can for formed and remain stable at approximately 100 V of source voltage and consume all the materials in their environment. With the combustion and ionization of the current-conducting contacts or electrodes, the current can continue to flow in the light arc in this case, although the current circuit is already mechanically disconnected by the switch, or should be disconnected. Various approaches are know that can be used in order to avoid these problems. Some of these approaches are also about the speed of the separation process.
Swiss patent CH 24 06 70 discloses a device for connecting and disconnecting electrical current circuits in which high potentials occur. The patent discloses that a contact element conducting a high voltage can be covered with a metallic shield cover. The contact conductor element can be provided with a plurality of individual contact conductors and accordingly, the metallic shield cover is provided with a number of openings corresponding to the number of the contact conductors. The shield cover is mechanically connected with the contact conductors, so that at the approach of a second contact, the opposite contact conductor is moved back and the contact conductors that were up until that point shielded are only then released through the openings. This switching device should be used in particular in power amplifiers of long-wave transmitters.
It will be appreciated that the formation of light arcs is complicated by the shield cover, but what is also apparent is that their formation cannot be suppressed completely in any case at a sufficiently high voltage. The mechanical design is also not very suitable for a very fast connection or disconnection of an electrical circuit. Moreover, it is effective only with relatively high-frequency currents.
The German patent document DE 19 28 922 C3 discloses an approach to high-voltage technology that also emphasizes mechanical separation of electrical circuits. The current is conducted through one or several disconnecting knives, which can be safely moved mechanically into a mating switch. The disconnecting knives can be additionally also rotated to obtain a better and more reliable electrical contact with the mating switch. This approach makes it possible to use very high voltages in the range of more than 10 kV, and even more than 100 kV. However, the mechanical separation is again quite slow, and in addition, mechanically complicated component parts must be provided, which also take up space in the design.
The German publication of examined patent application 1 050 858 discloses en electrical circuit breaker in the form of an explosive insulator. The explosive insulator is equipped with a chamber in which is located a hollow conductor portion, so that an explosive charge can be introduced therein. The conductor portion can be connected through contacts with power lines. The explosive charge can be ignited with any ignition device, for example with a filament. The hollow conductor portion can thus be blown so that an insulating distance is thus created. The formation of a light arc should be suppressed by a bag or a container that is filled with water. The water is partially evaporated by the heat of the explosion and it should therefore support the deletion of the light arc. An important advantage of the explosive insulator is that a very fast disconnection of a circuit can be achieved. However, the deletion of the light arc with water does not appear to be satisfactory and it could also lead to wetting of the surrounding component parts. It should be further also noted that an interruption of the switching circuit can be caused here by the explosive charge. A manual operation is not possible, which means that this is not a switch in the classical meaning of the word. An encapsulation of the device, which would enable the effect externally, is not possible because the blast fumes, the debris from the explosion and in particular the evaporating water would create overpressures that could not be controlled anymore with normal means, but could only be controlled with extremely strong, metallic wall thicknesses.
The German Utility Model Publication DE 20 2007 013 841 U1 discloses an electrical switching device that is equipped with a crankcase. The operation of the switching device is carried out mechanically via this crankcase, for example so that it can be switched from an open position into a closed position, Insulating gas is employed in order to suppress possible occurrences of light arc. In order to reliably suppress a light arc, this insulating gas must have a predetermined minimum pressure. A pressure sensor is provided to ensure that a minimum pressure is maintained. When an insulating gas appears to suppress reliably occurrences of light arc, for example with something like a water bag, this makes it very complicated to provide pressure sensors. In this regards, therefore, a simpler solution would be desirable.
German Unexamined Patent Application DE 198 19 662 A1 discloses an electrical switch for interrupting the power supply of a motor vehicle. The electrical circuit corresponds substantially to the concept of a disconnecting switch.
It should in particular serve to avoid short-circuiting in the electrical system in a motor vehicle in case of an accident. A similar short-circuit can cause fire when there is leaking fuel. That is why the electrical switch is inserted after the battery terminal. The electrical switch may be triggered for example with a squib, which in its turn is triggered by a crash or a collision sensor. A spark can occur when the switch is disconnected. This is to be shielded by the housing against the environment.
This electrical switch is designed for high currents and voltages, which can occur with a short-circuit in a battery or comparable short-circuiting in a motor vehicle. However, the generation of a spark cannot be completely avoided, which is why the housing must protect with reliability against this.
German patent application publication DE 102 05 369 B4 discloses a similar switch in the form of an electrical fuse, in particular a pyrotechnic fuse for interrupting high currents in electrical circuits. Also this fuse is designed to be used in particular to disconnect on-board wiring of an auto battery shortly after an accident. But also this improved approach does not allow for any kind of manual switching.
Although both last-named switches are well compatible with source voltages under 100 V of rectified voltage, light arc would still necessarily occur, which would remain stable in the moment of disconnection with high electrical currents, so that the switch would be destroyed but the circuit would ultimately not be disconnected.